1. Field of the Invention
The present invention relates to a fuel heating apparatus for an internal combustion engine and, more particularly, to an apparatus for heating and vaporizing the fuel which tends to flow in a liquid phase on the inner surface of the intake system of an internal combustion engine when it is at a low temperature.
2. Description of the Prior Art
The state which an internal combustion engine takes by the time the engine is sufficiently warmed up is called as "cold condition". In the cold condition, the vaporization of the fuel is not facilitated and a part of the fuel supply to the engine forms a liquid film on the inner surface of an intake manifold of the engine and flows slowly on the manifold inner surface. This adversely affects the mixture of the fuel and air, so that the air-fuel mixture produced is leaner than the air-fuel ratio which is required to assure smooth engine operation.
In order to overcome the problem discussed above, the internal combustion engine when in cold condition was supplied with the fuel in excess of the predetermined amount. The excessive fuel supply, however, disadvantageously increased the harmful components of the engine exhaust gases, such as HC, and deteriorated the fuel consumption rate of the engine.
So as to eliminate the disadvantages discussed, it has been proposed to dispose an electric heater at the bottom of the point of the intake manifold where the branches thereof diverge (this point of the intake manifold will be called as "diverging point"). Because the location of the heater has not been good, the operation of the heater to heat the air to be introduced into the engine has consumed a large amount of electric energy. The electric heater has caused a decrease in the charging effect and, in addition, has not been effective to remarkably improve the vaporization of the liquid fuel part flowing on the inner surface of the intake manifold.